ghcjs: don't propagate Cabal to all packages

Previously, we were compiling Setup.hs with ghcjs (instead of  ghc),
and that required that Cabal be available, otherwise the Setup.hs would
fail to compile.

Now that we are compiling Setup.hs with ghc, it's no longer necessary
to add Cabal as a dependency to all ghcjs packages.

pkgs/development/haskell-modules/configuration-ghcjs.nix

@@ -21,13 +21,6 @@ self: super:
     '';
   });
 
-  mkDerivation = drv: super.mkDerivation (drv // {
-    # Need Cabal lib to be available.
-    libraryHaskellDepends = drv.libraryHaskellDepends
-      # Be careful not to end up in infinite recursion!
-      ++ pkgs.lib.optional (!(builtins.elem drv.pname ["Cabal" "hscolour"])) self.Cabal;
-  });
-
   # LLVM is not supported on this GHC; use the latest one.
   inherit (pkgs) llvmPackages;